In a conventional gasoline powered internal combustion engine, gasoline is channeled through a fuel injector or carburetor, and then mixed with air to provide an air-to-fuel ratio of approximately 10:1 to 14:7:1. The gasoline and air mixture is then delivered into a combustion chamber and ignited by a spark generated by a spark plug. The conventional engine configuration is such that a substantial amount of gasoline is contained in the air/fuel mixture delivered into the combustion chamber, and the gasoline is not all consumed upon ignition by the spark plug's spark. As a result, the engine discharges exhaust containing unburned gasoline and other emissions, such as carbon monoxide, carbon dioxide, hydrocarbons, or nitrogen oxides (NO.sub.x), into the environment.
In most vehicles built after the late 1980s, a conventional on-board computer, also known as an electronic control module or ECM, is mounted to the vehicle and connected to the engine. The ECM controls and monitors a wide range of engine conditions, including the fuel flow and fuel delivery to the engine. The ECM also controls the air/fuel mixture's air-to-fuel ratio during different driving conditions. For example, the air-to-fuel ratio for normal driving when the throttle is partially open is 14.7:1. When additional power is needed and the throttle is wide open, such as when pulling a load up a hill, the ECM adjusts the air-to-fuel ratio to 12:1, so more fuel is used to achieve the necessary power increase. The ECM monitors multiple sensors in the engine and adjusts various operating parameters to maintain the air-to-fuel ratio at a selected value. The ECM also controls the engine's timing for spark generation to detonate the air/fuel mixture when the engine's pistons are at selected positions within the cylinders so as to achieve the desired power from the engine.
The ECMs have one or more computer chips, such as PROMs (Programmable-Read-Only Memory) that contain instructions and calibration data for operation of the engine. The computer chips provided by the vehicle's manufacturer, however, are programmed with factory settings for engine operation with conventional spark plugs to achieve an acceptable engine performance that provides sufficient power with reasonable fuel efficiency and acceptable engine emissions.
The conventional ECM has a computer chip or PROM that can be removed and replaced with a custom chip programmed with different instructions and calibration data to change and improve aspects of the engine's performance, such as power output. Other ECMs have reprogrammable PROM (e.g., Flash EEPROM) that can be reprogrammed with the different instructions and calibration data. For example, a custom computer chip or reprogramming includes instructions and calibration data for the ECM to increase the engine's power out, which typically results in decreased fuel efficiently and often unacceptably high engine emissions. Accordingly, these custom computer chips are typically illegal for street vehicles (e.g., non-racing or non-off road vehicles) unless expensive federal test procedures and other requirements are met.
The engine controlled by the ECM uses conventional spark plugs for ignition of the air/fuel mixture. The conventional spark plug has a 1.3 mm to 2.0 mm diameter center electrode that is spaced apart from a similarly sized ground electrode by approximately a 0.8 mm gap. The spark plug is connected to the vehicle's coil and when the voltage at the center electrode reaches the ionization point, the electrical charges jump the gap in the form of a spark. The spark plugs are typically driven by a conventional 15,000-30,000 volt coil which provides the necessary spark voltage that allows the spark to arc across the gap.
The conventional spark plug design is such that the spark generated is a relatively small, blue spark. This small blue spark usually provides enough heat to detonate the air/fuel mixture in the combustion chamber so as to drive one of the engine's pistons on the down stroke. While the conventional spark plugs allow the engine to run at what consumers consider acceptable levels, the spark plugs do not necessarily optimize the engine's performance. The spark plugs have relatively small gaps that requires less voltage to generate the spark, which results in a cool or lower power spark. This lower power spark ignites the air/fuel mixture with lower efficiency than a hot spark, so more fuel is required in the air/fuel mixture to achieve the desired power output from the engine. Accordingly, the engine operates with a lower fuel efficiency. In addition, the spark plugs inefficient ignition also results in an incomplete burn of the fuel, thereby resulting in higher engine emissions.
Many modifications to spark plugs and other engine components have been tried in an attempt to obtain increased power without unacceptable decreases in fuel efficiency and increases in emissions. As an example, Splitfire of Illinois, U.S.A. manufactures a spark plug having a standard center electrode that is spaced apart by a standard spark gap from a V-shaped ground electrode, which provides two areas to which a spark can arc. One goal of Splitfire's spark plug is to allow a spark to arc to each leg of the ground electrode to produce more spark for igniting the air/fuel mixture.
BERU of Germany produces for Nology Engineering, a Silverstone.TM. spark plug having a 2 mm diameter, silver center electrode for highly efficient conduction of current from the ignition coil through the spark plug. The silver center electrode is spaced apart from a standard ground electrode by a standard spark gap of approximately 0.8 mm. The Silverstone.TM. spark plugs are combined, however, with a higher voltage, retrofit ignition coil that provides an increased available spark voltage so as to create a more powerful and hotter spark than the thin blue spark of the other conventional spark plugs. Although the Silverstone.TM. spark plug provides a powerful and hotter spark, the spark plug requires the use of the higher voltage coil to obtain the greater power output by the conventional engine. A further drawback to the Silverstone.TM. spark plug is that the silver center electrode is relatively soft and generation of the more powerful, hotter spark results in a shorter useful life than other conventional spark plugs.
The conventional spark plug's center electrode also has a relatively small surface area from which sparks extend across the gap. The small surface area, however, is subject to more localized heat from spark generation during the spark plug's life, because the sparks can only be generated from that small area. As a result, the conventional spark plug's center electrode is worn over time, thereby reducing the spark plug's useful life.
The conventional spark plug's lower power spark and smaller surface area at the center electrode also results in a greater number of misfires. When the spark plug misfires, a proper spark is either not provided or the spark does not ignite the air/fuel mixture for that cycle. Accordingly, a misfiring spark plug reduces the engine's fuel efficiency and power output and increases the engine's emissions.
The conventional spark plug also causes relatively high exhaust temperatures, which causes the engine to run hotter, thereby requiring cooling systems and the like for the engine. These higher temperatures are caused by the spark plug because the lower power spark provides less heat, so less of the air/fuel mixture is ignited simultaneously at the beginning of the air/fuel mixture's detonation. As a result, the flame from growth through the air/fuel mixture is slower, so more time is required to detonate the mixture in the combustion chamber. This longer detonation period results in more heat energy that is not converted to kinetic energy, so the combustion exhaust is hotter, which results in higher engine operating temperature. These higher engine operating temperatures require that the engine's components be made of materials that can withstand the higher operating temperatures, which typically increase the engine's cost and weight.